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| United States Patent |
5,064,914
|
|
Rosenquist
, et al.
|
November 12, 1991
|
Method of branching polyesters
Abstract
Linear polyester are branched by transesterification with resins having
repeating or recurring polymer chain units of the formula:
##STR1##
wherein m, n and p are each independent integers of 0 or 1; R represents
hydrocarbyl; and E represents alkylene containing from 1 to 15 carbon
atoms, inclusive, halogen- substituted alkylene of 1 to 15 carbon atoms,
inclusive, alkylene of 1 to 15 carbon atoms, inclusive, substituted with a
--COOR group where R is as previously defined, or alkylene having 1 to 15
carbon atoms substituted with a monovalent group of the formula:
##STR2##
wherein X represents one of hydrogen, hydrocarbyl or
##STR3##
wherein R is as defined above; provided there is at least one moiety
present, containing an R group.
| Inventors:
|
Rosenquist; Niles R. (Evansville, IN);
Bostick; Edgar E. (Mt. Vernon, IN)
|
| Assignee:
|
General Electric Company (Mt. Vernon, IN)
|
| Appl. No.:
|
447492 |
| Filed:
|
December 7, 1989 |
| Current U.S. Class: |
525/439; 525/444 |
| Intern'l Class: |
C08L 067/02; C08G 063/91 |
| Field of Search: |
525/439,444
|
References Cited
U.S. Patent Documents
| 4132707 | Jan., 1979 | Borman | 525/444.
|
| 4826928 | May., 1989 | Rosenquist | 525/439.
|
Primary Examiner: Short; Patricia
Attorney, Agent or Firm: Barancik; Martin B., Eisele; Joseph T.
Claims
What is claimed is:
1. A process for branching a thermoplastic, linear, polyester resin, which
comprises;
providing said resin;
homogeneously mixing with the resin, a branching proportion of a
thermoplastic, polymeric, branching resin having recurring polymer chain
units selected from those of the formula:
##STR20##
wherein m, n and p are each independent integers of 0 or 1; R represents
hydrocarbyl; and E represents alkylene containing from 1 to 15 carbon
atoms, inclusive, halogen--substituted alkylene of 1 to 15 carbon atoms,
inclusive, alkylene of 1 to 15 carbon atoms, inclusive, substituted with
a--COOR group where R is as previously defined, or alkylene having 1 to 15
carbon atoms substituted with a monovalent group of the formula:
##STR21##
wherein X represents one of hydrogen, PG,30 hydrocarbyl or
##STR22##
wherein R is as defined above; provided there is at least one moiety
present, containing an R group; and
effecting a branching transesterification reaction of the linear polyester
resin with the branching resin.
2. The process of claim 1 wherein m is 1 and n is 0.
3. The process of claim 2 wherein R represents alkyl.
4. The process of claim 1 wherein m, n and p are each 1.
5. The process of claim 4 wherein E represents alkylene and R is alkyl.
6. The process of claim 4 wherein m and p are each 0; n is 1; E represents
alkylene substituted with a--COOR group and R is alkyl.
7. The process of claim 1 wherein the linear polyester resin has repeating
chain units of the formula:
##STR23##
wherein each of R.sup.1 and R.sup.2 is a divalent aliphatic, alicyclic or
aromatic radical containing 2 to 10 carbon atoms.
8. The process of claim 1 wherein the reaction is promoted with a catalyst.
9. The branched product of claim 1.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to polyester resins and more particularly to a method
of branching linear polyester resins.
2. Brief Description of the Prior Art
Linear polyesters such as, for example, poly (ethylene terephthalate)
(referred to hereafter at times as "PET") and poly (1,4-butylene
terephthalate) (referred to hereafter at times as "PBT") are widely known
and used to fabricate a variety of thermoplastic articles; see for example
U.S. Pat. No. 4,684,686. Many of their properties, including chemical
stability and solvent resistance make them attractive candidates for such
forming operations as blow molding, profile extrusion and thermoforming.
One problem in such operations is the relatively low melt viscosities of
the polyesters, as a result of which the formed articles do not always
adequately retain their shape immediately after forming and before they
have cooled.
One method of increasing the melt viscosity of a linear polyester,
described in U.S. Pat. No. 4,590,259, is to substantially increase its
molecular weight. This is possible (though often difficult, owing to the
crystallinity of the polyester) if the polyester has a low proportion of
carboxylic acid end groups. However, many polyesters currently available
have a relatively high proportion of such groups, which makes molecular
weight increase impractical as a means of increasing melt viscosity. In
any event, specialized equipment is usually required to increase a
polyester's molecular weight.
Even if the polyester molecular weight is high, melt behavior often leaves
something to be desired since it is essentially independent of shearing
stresses imposed during forming. In the best situation, a resin suitable
for blow molding, profile extrusion, thermoforming and the like will
exhibit a non-Newtonian response, having a low viscosity under high shear
conditions such as those encountered during extrusion and a high viscosity
under conditions of low shear typical of a blow molded parison or a
thermoformed article. High molecular weight polyesters under melt
conditions have the disadvantage of being essentially Newtonian in their
behavior.
The present invention achieves thermomolding compositions exhibiting higher
melt strengths by a branching of the polyester, which can take place
during the forming process, for example during extrusion.
An advantage of the present invention it that it does not require specially
designed facilities for polyester production. Conventional processing
equipment may be employed for the branching of conventional polyesters
such as PET, PBT and like elastomeric polyesters.
SUMMARY OF THE INVENTION
The invention comprises a process for branching a thermoplastic, linear,
polyester resin, which comprises;
providing the resin;
homogeneously mixing with the resin, a branching proportion of a
thermoplastic, polymeric, branching resin having recurring polymer chain
units selected from those of the formula:
##STR4##
wherein m, n and p are each independently integers of 0 or 1; R
represents hydrocarbyl; and E represents alkylene containing from 1 to 15
carbon atoms, inclusive, halogen--substituted alkylene of 1 to 15 carbon
atoms, inclusive, alkylene of 1 to 15 carbon atoms, inclusive, substituted
with a--COOR group where R is as previously defined, or alkylene having 1
to 15 carbon atoms substituted with a monovalent group of the formula:
##STR5##
wherein X represents one of hydrogen, hydrocarbyl or
##STR6##
wherein R is as defined above; provided there is at least one moiety
present, containing an R group; and
effecting a branching reaction between the linear polyester resin and the
branching resin.
The term "hydrocarbyl" as used herein means the monovalent moiety obtained
upon removal of a hydrogen atom from a parent hydrocarbon. Representative
of aliphatic hydrocarbyl are alkyl of 1 to 15 carbon atoms, inclusive such
as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl,
decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl and isomers
thereof; cycloalkyl of 3 to 8 carbon atoms, inclusive, such as
cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl;
alkyl substituted cycloalkyl of 4 to 15 carbon atoms, inclusive, such as
2-methylcyclopropyl, 3,4-dimethylcyclohexyl; alkenyl of 2 to 15 carbon
atoms, inclusive, such as allyl, 3-hexenyl, 2,4-pentadienyl; aryl and
aralkyl of 7 to 15 carbon atoms, inclusive, such as benzyl, phenethyl,
phenpropyl, phenbutyl, phenoctyl and the like.
The term "halogen" is used throughout the specification and claims in its
normally accepted sense as embracive of chlorine, bromine, iodine and
fluorine.
The term "alkylene" as used herein means the divalent moiety obtained upon
removal of two hydrogen atoms from a parent hydrocarbon. Representative of
alkylene are methylene, propylene, butylene, decylene, tetradecylene,
pentadecylene and isomeric forms thereof.
The invention also comprises novel polyester branching resins, useful in
the method of the invention and branched linear polyester resins prepared
by the method of the invention.
The branched polyester products of the method of the invention are
characterized-in-part by an enhanced melt strength and melt elasticity.
Other advantageous physical properties will be described below. The
branched polyesters of the invention are useful in applications such as
profile extrusion (for example of wire and cable insulation, extruded
bars, pipes, fiber optic buffer tubes, and sheets); blowmolding (for
example of containers and cans, gas tanks, automotive exterior
applications such as bumpers, aerodams, spoilers and ground effects
packages); and thermoforming (for example of automotive exterior
applications and food packaging).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
The linear polyesters advantageneously crosslinked according to the process
of the invention are well known synthetic polymers as are the methods of
their preparation. Many of these polyesters are commercially available.
Representative of the linear polyesters used in the process of the
invention are those having repeating chain units of the formula:
##STR7##
wherein each of R.sup.1 and R.sup.2 is a divalent aliphatic, alicyclic or
aromatic radical containing about 2-10 carbon atoms. At least about 30 of
said units are usually present with at least about 50 being preferred,
most preferably at least about 100. Such linear polyesters are typically
prepared by the known reaction of dihydroxy compounds with dicarboxylic
acids or functional derivatives thereof such as anhydrides, acid chlorides
or lower alkyl (especially methyl) esters, preferably the esters; see for
example U.S. Pat. Nos. 2,465,319; 2,720,502; 2,727,881 2,822,348;
3,047,539; 3,671,487; 3,953,394; and 4,128,526, all of which are
incorporated herein by reference thereto.
The R.sup.1 radical may be derived from such dihydroxy compounds as
ethylene glycol, 1,4-butanediol (both of which are preferred), propylene
glycol, 1,3-propanediol, 1,6-hexanediol, 1,10-decanediol,
1,4-cyclohexanedimethanol, 2-butene-1,4-diol, resorcinol, hydroquinone,
bisphenol A and like dihydroxy compounds. They may also be radicals
containing substituents which do not substantially alter the reactivity of
the dihydroxy compound (e.g., alkoxy, halo, nitrile) or hetero atoms
(e.g., oxygen or sulfur).
The R.sup.2 radicals may be derived from such acids as succinic, adipic,
isophthalic and terephthalic acids or like substituted and hetero
atom-containing acids. They preferably contain about 6-10 carbon atoms,
inclusive.
Preferably, R.sup.1 is aliphatic and especially saturated aliphatic and
R.sup.2 is aromatic. The polyester is most desirably a poly(alkylene)
terephthalate, particularly poly(ethylene) terephthalate or
poly(1,4-butylene terephthalate) hereinafter sometimes referred to as
"polybutylene terephthalate" or "PBT".
PBT, because of its very rapid crystallization from molds is uniquely
useful as a component in injection moldable compositions. Accordingly, PBT
branched in accordance with the present invention, particularly by blow
molding technique, is particularly advantageous for the fabrication of
articles when certain properties are of importance. Work pieces molded
from such polyester resins, in comparison with other thermoplastics, offer
a high degree of surface hardness and abrasion resistance, high gloss and
low surface friction, in addition to enhanced fire resistance.
The polyesters branched by the method of the invention preferably have melt
viscosities within the range of from 7,000 to 75,000 poise, measured at
250.degree. C.
Certain of the branching resin agents employed in the process of the
invention are polyesters characterized-in-part by occasional recurring
chain units of the formula (I) given above. These branching agents are
advantageously selected from polyesters having repeating or frequently
recurring polymer chain units of the formula (II) given above, interrupted
by occassional chain units of the formula (I) given above. These branching
agents may be prepared by modifying the preparative procedure used to
prepare the linear polyesters, which are branched by the process of the
invention and already described above. The modification consists of
replacing a proportion of the dihydroxy reactant conventionally used and
described above with an equal equivalent proportion of a dihydroxy phenol
of the formula:
##STR8##
wherein R, E, m, n and p have the meanings previously ascribed to them.
Dihydroxy phenol compounds of the formula (III) are generally well know
compounds as are methods of their preparation. Representative of the
dihydroxy phenols of formula (III) are:
3,5-dihydroxy benzoic acid methyl, ethyl, propyl, isopropyl, butyl,
isobutyl, pentyl, hexyl, cyclopentyl, cyclohexyl, heptyl, octyl, nonyl,
decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl and phenyl
ester; the corresponding esters of
2,2-bis (4-hydroxyphenyl) butyric acid;
4,4-bis (4-hydroxyphenyl) valeric acid;
4,4-bis (3-methyl-4-hydroxyphenyl) valeric acid; and
3,3-bis (4-hydroxyphenyl) caproic acid.
Preferred phenol (III) compounds for preparing the polyester branching
resin agents used in the process of the invention include those of the
more specific formula:
##STR9##
wherein E and R are as previously defined.
The diphenol esters of the Formula (IV) are generally well known as are
methods of their preparation; see for example U.S. Pat. No. 3,285,875. In
general, they may also be prepared by esterifying the corresponding
dihydroxy diacids, i.e.; the diphenolacids of the Formula (IV) wherein R
is hydrogen, with an appropriate alcohol of the formula:
##STR10##
wherein R' represents hydrocarbyl or halogen-substituted hydrocarbyl, in
the presence of an esterification catalyst such as an organic acid. The
esterification is advantageously carried out in the presence of an inert
organic solvent for the reactants and the ester product or a large excess
of the alcohol (V). The ester product is separated from the reaction
mixture by conventional techniques of extraction, washing and solvent
removal. Alternatively, the esters of formula (IV) may be prepared by the
general method described in British Patent specification 952,591.
Alcohols of the Formula (V) given above are generally well known and
include, for example, cyclohexyl alcohol, 4-tert-butyl-cyclohexyl alcohol
and, preferably, methyl alcohol, isopropyl alcohol or ethyl alcohol. Also
useful are the halogen-substituted hydrocarbon alcohols.
The phenol (III) compounds wherein E represents alkylene of 1 to 15 carbon
atoms substituted with a monovalent group of the formula:
##STR11##
wherein X is
##STR12##
are also well known compounds as are methods of their preparation. For
example, the phenol (III) compounds of the formula:
##STR13##
may be prepared by the reaction of the corresponding
trishydroxyphenylethane with phenyl chloroformate.
The branching resins used in the process of the invention also include
polycarbonate resins, i.e.; resins containing repeating or recurring
polycarbonate units of the formula:
##STR14##
wherein D is a divalent aromatic radical of a dihydric phenol (III)
employed in the polymerization reaction, which comprises the reaction of
the dihydric phenol (III) with a carbonate precursor. The reaction is well
known and is described for example in the U.S. Pat. Nos. 3,028,365;
3,334,154; 3,275,601; 3,915, 926; 3,030,331; 3,169,121; and 3,027,814;
Although the reaction conditions of the preparative processes may vary, the
interfacial polymerization processes typically involve dissolving or
dispersing the phenol reactant in a suitable water immiscible solvent
medium and contacting the reactants with the carbonate precursor, such as
phosgene, in the presence of a suitable catalyst and an aqueous caustic
solution under controlled pH conditions. The most commonly used water
immiscible solvents include methylene chloride, 1,1-dichloroethane,
chlorobenzene, toluene, and the like.
The catalyst employed accelerates the rate of polymerization of the
dihydric phenol (III) reactant with the carbonate precursor.
Representative catalysts include but are not limited to tertiary amines
such as triethylamine, quaternary phosphonium compounds, quaternary
ammonium compounds, and the like. The preferred process for preparing
polycarbonate branching agent resins comprises a phosgenation reaction.
The temperature at which the phosgenation reaction proceeds may vary from
below 0.degree. C., to above 100.degree. C. The phosgenation reaction
preferably proceeds at temperatures of from room temperatures (25.degree.
C.) to 50.degree. C. Since the reaction is exothermic, the rate of
phosgene addition and solvent reflux may be used to control the reaction
temperature. The amount of phosgene required will generally depend upon
the amount of the dihydric phenol (III) and the amount of any dicarboxylic
acid also present.
The carbonate precursor employed in the preparation of known polycarbonate
resins as well as resins having chains including the moieties of Formula
(I) may be a carbonyl halide, a diarylcarbonate, or a bishaloformate. The
carbonyl halides include carbonyl bromide, carbonyl chloride, and mixtures
thereof. The bishaloformates include the bischloroformates of ethylene
glycol, neopentylene glycol, polyethylene glycol, and the like. Typical of
diarylcarbonates which may be employed are diphenyl carbonate, and the
di(alkylphenyl)-carbonates such as di(tolyl) carbonate. Some other
non-limiting illustrative examples of suitable diarylcarbonates include
di(napthyl)carbonate, phenyl tolyl carbonate, and the like.
The preferred carbonate precursors are the carbonyl halides, with carbonyl
chloride, also known as phosgene, being the preferred carbonyl halide.
In the preparation of embodiment polycarbonate branching resins used in the
process of the invention, a portion of the dihydroxy phenol (III) reactant
is replaced with an equivalent proportion of a second dihydric phenol,
represented by those of the formula:
##STR15##
wherein A is selected from the group consisting of a divalent hydrocarbon
radical containing from 1 to about 15 carbon atoms; a halogen-substituted
divalent hydrocarbon radical containing from 1 to about 15 carbon atoms
and divalent groups such as:
##STR16##
Each X in the Formula (VII) is independently selected from the group
consisting of halogen, hydrocarbyl such as an alkyl group of from 1 to
about 8 carbon atoms; an aryl group of from 6-18 carbon atoms, an aralkyl
group of from 7 to about 14 carbon atoms, an oxyalkyl group of from 1 to
about 8 carbon atoms, and an oxyaryl group of from 6 to 19 carbon atoms;
and wherein m is zero or 1 and y is a whole number integer of from 0 to 4,
inclusive.
Typical of some of the dihydric phenols (VII) that are advantageously
employed are bis-phenols such as bis(4-hydroxyphenyl) methane,
2,2'-bis-(4-hydroxy-3-methylphenyl)propane,
4,4'-bis(4-hydroxyphenyl)-heptane,
2,2'-bis(4-hydroxy-3,5-dichlorophenyl)propane,
2,2'-bis(4-hydroxy-3,5-dibromophenyl)propane; dihydric phenol ethers such
as bis(4-hydroxphenyl)ether, bis(3,5-dichloro-4-hydroxyphenyl)ether;
dihydroxydiphenols such as 3,3'-dichloro-4,4'-dihydorxybiphenyl;
dihydroxyaryl sulfones such as bis(4-hydroxyphenyl) sulfone,
bis(3,5-dimethyl-4-hydroxyphenyl)sulfone; dihydroxybenzenes, such as
resorcinol and hydroquinone; halo- and alkyl-substituted dihydroxy
benzenes such as 1,4-dihydroxy-2,5-dichlorobenzene,
1,4-dihydroxy-3-methylbenzene; and dihydroxy diphenyl sulfides and
sulfoxides such as bis(4-hydroxyphenyl)-sulfide and bis(4-hydroxyphenyl)
sulfoxide. A variety of additional dihydric phenols are also available and
are disclosed in U.S. Pat. Nos. 2,999,835; 3,028,365 and 3,153,008, all of
which are incorporated herein by reference. It is, of course, possible to
employ two or more different dihydric phenols (VII) or a combination of a
dihydric phenol (VII) with glycol.
Preferred dihydric phenols of Formula (VII) are the 4,4'-bisphenols.
Those polycarbonate resins used as cross-linker agents in the process of
the invention, wherein dihydric phenols of the formula (VII) are secondary
reactants in their preparation, will of course contain polymer chain units
of the formula (VI) given above, but wherein D represents a divalent
aromatic radical of the dihydric phenol (VII).
The term "polycarbonate" as used herein is also inclusive of
copolyester-polycarbonates, i.e.; resins which contain in addition to
recurring polycarbonate chain units of Formula (VI) given above, wherein D
represents the divalent aromatic radical of the dihydric phenol (III) and
optionally of the dihydric phenol (VII), repeating or recurring
carboxylate units, for example of formula:
##STR17##
wherein R.sup.3 is a divalent hydrocarbylene group such as an alkylene,
alkylidene, or cycloalkylene group; an alkylene, alkylidene or
cycloalkylene group containing ethylenic unsaturation; an aromatic group
such as phenylene, biphenylene, and the like; two or more aromatic groups
connected through non-aromatic linkages such as alkylene or alkylidene
groups; and a divalent aralkyl radical such as tolylene, xylylene, and the
like,
The copolyester-carbonate branching agent resins used in the method of the
invention include some which are generally well known; see for example the
U.S. Pat. No. 4,788,274 (Rosenquist) incorporated herein by reference
thereto. In general, they are prepared as described above for the
preparation of polycarbonate branching agents, but by the added presence
of a difunctional carboxylic acid (ester precursor) in the water
immiscible solvent; see for example U.S. Pat. Nos. 3,169,121 and 4,487,896
incorporated herein by reference thereto.
In general, any difunctional carboxylic acid (dicarboxylic acid)
conventionally used in the preparation of linear polyesters may be
utilized in the preparation of the copolyester-carbonate resin branching
agents of the instant invention. Generally, the difunctional carboxylic
acids which may be utilized include the aliphatic carboxylic acids, the
aromatic carboxylic acids, and the aliphatic-aromatic carboxylic acids.
These acids are well known and are disclosed for example in U.S. Pat. No.
3,169,121, which is hereby incorporated herein by reference.
Representative of such difunctional carboxylic acids are difunctional
carboxylic acids of the formula:
##STR18##
wherein R.sup.3 has the meaning previously ascribed to it.
Preferred difunctional carboxylic acids employed are the aromatic
dicarboxylic acids. Particularly useful aromatic dicarboxylic acids are
those represented by the general formula:
##STR19##
wherein j is a positive whole integer having a value of from 0 to 4
inclusive; and each R.sup.4 is independently selected from the group
consisting of alkyl radicals, preferably lower alkyl radicals (containing
from 1 to about 5 carbon atoms).
Mixtures of these difunctional carboxylic acids may be employed as well as
single acids. Therefore, where the term difunctional carboxylic acid is
used herein it is to be understood that this term includes mixtures of two
or more different difuntional carboxylic acids as well as individual
carboxylic acids.
Most preferred as aromatic dicarboxylic acids are isophthalic acid,
terephthalic acid, and mixtures thereof. A particularly useful
difunctional carboxylic acid comprises a mixture of isophthalic acid and
terephthalic acid wherein the weight ratio of terephthalic acid to
isophthalic acid is in the range of from about 10:1 to about 0.2:9.8.
Rather than utilizing the difunctional carboxylic acid per se, it is
possible, and sometimes even preferred, to employ the reactive derivatives
of said acid. Illustrative of these reactive derivatives are the acid
halides. The preferred acid halides are the acid dichlorides and the acid
dibromides. Thus, for example, instead of using isophthalic acid,
terephthalic acid or mixtures thereof, it is possible to employ
isophthaloyl dichloride, terephthaloyl dichloride, and mixtures thereof.
It should be understood then that the term "difunctional carboxylic acid"
as used herein, includes the reactive derivatives.
The proportions of reactants employed to prepare the copolyester-carbonate
resin branching agents of the invention will vary in accordance with the
proposed use of the product resin. Those skilled in the art are aware of
useful proportions, as described in the U.S. patents referred to above. In
general, the amount of the ester bonds may be from about 5 to about 90
mole percent, preferably from about 35 to about 80 mole percent, relative
to the carbonate bonds. For example, 5 moles of bisphenol-A reacting
completely with 4 moles of isophthaloyl dichloride and 1 mole of phosgene
would give a copolyester-carbonate of 80 mole percent ester bonds.
Also included within the scope of the instant invention are randomly
branched polycarbonate branching resins wherein a minor amount [typically
between 0.05 and 2 mole percent, based on the quantity of dihydric phenol
(III) and (VII) used] of a polyfunctional aromatic compound is a
co-reactant with the dihydric phenol (VII) in the reaction mixture,
comprising also the carbonate precursor and optionally the ester
precursor; to provide a thermoplastic randomly branched, branching agent
polycarbonate. These polyfunctional aromatic compounds may be hydroxyl,
carboxyl, carboxylic anhydride, haloformyl, or mixtures thereof. Some
illustrative non-limiting example of these polyfunctional compounds
include trimellitic anhydride, trimellitic acid, trimellityl trichloride,
4-chloroformyl phthalic anhydride, pyromellitic acid, pyromellitic
dianhydride, mellitic acid, mellitic anhydride, trimesic acid,
benzophenonetetracarboxylic acid, benzophenonetetracarboxylic acid
anhydride, and the like. Other organic polyfunctional compounds useful in
making randomly branched polycarbonates are disclosed in U.S. Pat. Nos.
3,635,895 and 4,001,184, both of which are incorporated herein by
reference.
In the conventional polymerization methods of preparing polycarbonates, a
molecular weight regulator (a chain stopper) is generally added to the
reaction mixture prior to or during the contacting with a carbonate
precursor. Useful molecular weight regulators include, but are not limited
to, monohydricphenols such as phenol, chroman-I, paratertiarybutyl-phenol,
p-cumylphenol and the like. Techniques for the control of molecular weight
are well known in the art and used for controlling the molecular weight of
the polycarbonate branching agent resins used in the present invention.
In accordance with the process of the invention, a branching resin as
described above is homogeneously admixed with the linear polyester to be
branched. Admixture may be carried out with the aid of conventional resin
mixing apparatus, including but not limited to conventional resin
extruders equipped to mix two different resin materials, dry mixers and
the like. The solid resins may be pre-mixed before introduction into the
extruder.
A branching proportion of the branching resin will depend upon the density
of branches desired and the number of branch sites available. In general,
from about 0.1 to 25 percent by weight of the linear polyester, will
comprise a branching proportion of branching agent resin.
The thermoplastic molding resin compositions of the instant invention
containing branching resins having units of the formula (I) may also be
admixed with various commonly known and used additives such as, for
example, antioxidants; antistatic agents; inert filler such as glass,
talc, mica, and clay; ultraviolet radiation absorbers such as the
benzophenones, benzotriazoles, and the like; hydrolytic stabilizers such
as the epoxides disclosed in U.S. Pat. Nos. 3,489,716, 4,138,379 and
3,839,247, all of which are incorporated herein by reference; color
stabilizers such as the organophosphites; thermal stabilizers such as
phosphite; flame retardants; and mold release agents.
The actual branching of the linear polyester resin is effected
advantageously by a transesterification reaction. The transesterification
reaction is promoted by heating the mixed reactant resins to a
transesterification temperature (generally within the range of from about
100.degree. to 300.degree. C., preferably 200.degree. to 250.degree. C.).
A catalytic proportion of a transesterification catalyst may be present to
promote the exchange. A catalytic proportion is generally one within the
range of from about 0.00001 to 0.01 parts by weight of the resin
composition. Useful transesterfication catalysts are basic catalysts
conventionally employed in transesterification reactions. Representative
of such catalysts are oxides, hydrides, hydroxides or amides of alkali or
alkaline earth metals such as, for example, lithium hydroxide and the
like. Also, basic metal oxides such as zinc oxide, and the like. Also
representative of transesterification catalysts are salts of weak acids
such as lithium stearate; organotin catalysts such as dibutyltin oxide;
aluminum or boron anion containing catalysts such as those described in
U.S. Pat. Nos. 4,330,669 and 4,395,062 and the like. One or more catalysts
may be used in combination.
Although the invention is not to be bound by any theory of operation, it is
believed that during the transesterification reactions, the R groups are
displaced by catalyst activated polymer end groups to yield new polymer
branch sites.
The following examples and preparations describe the manner and process of
making and using the invention and set forth the best mode contemplated by
the inventor of carrying out the invention but are not to be construed as
limiting the invention. Where reported, the following tests were carried
out:
Intrinsic Viscosity (IV)
The intrinsic viscosity of polycarbonates was measured at a temperature of
25.degree. C. in methylene chloride and is reported in deciliters/gram
(dl/g).
Preparation 1
Preparation of 1/1 copolycarbonate of bisphenol-A (BPA) and methyl-2,
4-dihydroxybenzoate.
A 2000 ml four neck flask was fitted with a mechanical stirrer, a pH probe,
an aqueous caustic inlet tube and a Claisen adaptor to which was attached
a dry ice condenser and a gas inlet tube. To the flask was added 700 ml
methylene chloride, 200 ml water, 8.4 ml (0.06 mole) triethylamine, 57 g
(0.25 mole) bisphenol-A and 42 g (0.25 mole) of methyl-2,
4-dihydroxybenzoate. With stirring, the pH was raised to 9 to 10 by
addition of 25% aqueous sodium hydroxide, then phosgene was introduced
into the flask at 1.5 g/min for 50 minutes, at which time an additional
350 ml of water and 150 ml of methylene chloride were added. Phosgene
addition was then continued for an additional 5 min (82.5 g, 0.83 mole
total phosgene) at which time the reaction mixture had become too viscous
to stir. After addition of 300 ml more of methylene chloride, the resins
layer was separated from the brine layer, washed with 3 wt. % aqueous HCl,
then twice with distilled water. The resins layer was then dried over
silica gel, filtered, then precipitated into two volumes of methanol in a
Waring blender, washed with additional methanol and dried. The resin was
found to have an intrinsic viscosity of 0.672 dl/g in methylene chloride
(25.degree. C.). The resin had a PMR spectrum consistent with the assigned
structure.
Preparation 2
Preparation of homopolycarbonate of methyl-2,4-dihydroxybenzoate. To the
apparatus as described above in Preparation 1, supra. was added 350 ml
methylene chloride, 100 ml water and 42 g (0.25 mole) of
methyl-2,4-dihydroxybenzoate. With stirring, phosgene was introduced into
the flask at a rate of 1.5 g/min for 30 mins (45 g, 0.45 mole) with the pH
maintained at 2.5 to 4 by the addition of 25% aqueous sodium hydroxide.
6.0 ml (0.043 mole) triethylamine was then added dropwise to the flask and
the pH then raised gradually to 9. Heat was evolved and the resin solution
became very viscous. Phosgene was then introduced for an additional 12
minutes at 1 g/min (12 g.; 0.12 mole) at pH 8.5 to 9, with simultaneous
addition of 300 ml additional methylene chloride. The resin layer was then
separated from the brine layer, washed with 3% aqueous HCl, then twice
with distilled water. The resin layer was then dried over magnesium
sulfate, filtered, precipitated into two volumes of methanol in a Waring
blender, washed with additional methanol and dried. The resin was found to
have an intrinsic viscosity of 0.551 in methylene chloride at 25.degree.
C. The resin had a PMR spectrum consistent with the assigned structure.
EXAMPLE 1
290 g of poly(butylene) terephthalate (Valox.RTM. 315 resin, General
Electric Co.), 10.9 g (2.0 mole %) of the 1/1 copolycarbonate of
bisphenol-A and methyl-2,4-dihydroxybenzoate (IV=0.672 dl/g) prepared
according to Preparation 1., supra. and 0.4 g (0.0014 mole %) of a lithium
stearate catalyst concentrate (prepared by extruding 13.6 g lithium
stearate into 980 g Valox.RTM. 315, supra., and 20 g Lexan.RTM. 145, a
polycarbonate resin available from the General Electric Co.) were blended
together, extruded and pelletized, using a 3/4" diameter Brabender single
screw extruder set at 250.degree. C. Residence time in the extruder was
estimated to be one minute. A portion of the extruded pellets were dried
and re-extruded. Melt viscosities at 250.degree. C. were determined, with
the initial Valox.RTM. 315 sample, the once extruded and twice extruded
samples exhibiting melt viscosities of 8070 poise, 30,700 poise and 32,100
poise, respectively, determined by the procedure of test ASTM D1238,
condition T with 0.042 inch orifice, 21500 g weights and at 250.degree. C.
EXAMPLE 2
1200 g of Valox.RTM. 315 resin, supra., 10.6 g (1.0 mole %) of a
homopolycarbonate of methyl-2,4-dihydroxybenzoate (prepared according to
the procedure of Preparation 2,supra. and 1.66 g (0.0014 mole %) of the
lithium stearate catalyst concentrate (described above In Example 1,
supra.) were blended together, extruded and pellitized using a 13/4"
diameter sterling single screw extruder set at 260.degree. C. Residence
time in the extruder was estimated to be one minute.
The extrusion was then repeated using 21.2 g (2 mole %) of the
homopolycarbonate. Melt viscosities at 250.degree. C. were determined as
described in Example 1, supra. with the initial Valox.RTM. 315 sample, the
1 mole % and the 2 mole % samples exhibiting 7880 poise, 14,900 poise and
33,700 poise, respectively.
Samples of the three materials were then injection molded at 250.degree. C.
into 25 mm diameter, 2.5 mm thick disks. Full rheology characterization of
these samples was then carried out on a Rheometrics Corp. Model RDS7700
dymanic spectrometer. Testing was at 240.degree. C., at 20% strain and
with 2.0 mm gap and 12.5 mm radius sample geometry. Initial time sweep
testing showed the samples to be stable under the test conditions. Results
of frequency sweep studies are given in Table I, below.
TABLE I
__________________________________________________________________________
Viscosity Characterization of Polybutylene Terephthalate
co-reacted with Ester Side Group (ESG) Polycarbonate Resin
.eta. (poise .times. 10.sup.-3).sup.1
G' (dyme/cm.sup.2 .times. 10.sup.-3).sup.2
G" (dyme/cm.sup.2 .times. 10.sup.-3).
sup.3
Resin 10 100 10 100 10 100
Composition 1 rad/s.sup.4
rad/s
rad/s
1 rad/s
rad/s
rad/s
1 rad/s
rad/s
rad/s
__________________________________________________________________________
Valox .RTM. 315-control
12.4 11.8
8.82
0.527
12.3
311.0
12.4
117.0
826.0
Valox .RTM. 315/1.0 mole %
36.8 31.1
15.2
2.77
71.9
781.0
36.7
302.0
1300.0
ESG Homopolymer
Valox .RTM. 315/2.0 mole %
147.0
81.8
28.8
53.0
403.0
1980.0
137.0
711.0
2090.0
ESG Homopolymer
__________________________________________________________________________
.sup.1 Complex Viscosity
.sup.2 Elastic Modulus
.sup.3 Viscous Modulus
.sup.4 Frequency (empirically equivalent to shear rate)
EXAMPLE 3
Torque Experiment Procedure: Torque experiments were carried on a System 90
torque rheometer manufactured by the Haake Buchler Instruments Co.,
Experiments were run at 50 rpm and 250.degree. C. set temperature
(250.degree. to 260.degree. C. actual temperature). 56.9 g samples of a
poly(butylene)terephthalate (Valox.RTM. 315 grade, General Electric Co.;
containing 100 ppm of titanium, the residue of the tetralkyl-titanate used
in its manufacture) were placed in the apparatus, and the sample mixed for
three minutes, to allow temperature and torque to stabilize. The ester
side group polycarbonate branching resin and transesterification catalyst
were then added, and the sample allowed to mix for an additional 17
minutes, with torque and temperature continuously monitored. Using this
procedure, the Preparations 1 and 2 above were tested. The test results
are given in Table II, below.
TABLE II
__________________________________________________________________________
Co-reaction of Polybutylene Terephthalate with the Ester Side Group
(ESG)
Polycarbonate Resin in the Haake Torque Rheometer
Polycarbonate Resin
Lithium
Level.sup.1
Stearate
Torque (Meter/grams)
Composition
(mole %)
(mole %).sup.2
Initial.sup.3
Maximum
(time)
Final
__________________________________________________________________________
--.sup.4 -- -- 482 none 285
--.sup.5 -- 0.001%
497 none 280
Lexan .RTM. 145 resin.sup.6
2.1 g (0%)
0.001%
528 none 280
1/1 ESG Co-Polymer.sup.7
2.1 g (2%)
-- 468 none 333
1/1 ESG Co-Polymer
2.1 g (2%)
0.05% 442 1077 (5.6)
630
1/1 ESG Co-Polymer
2.1 g (2%)
0.025%
494 1072 (5.2)
656
1/1 ESG Co-Polymer
2.1 g (2%)
0.002%
456 1202 (9.2)
865
1/1 ESG Co-Polymer
2.1 g (2%)
0.001%
477 1260 (7.6)
788
ESG Homopolymer.sup.8
1.0 g (2%)
0.002%
473 1086 (9.6)
758
ESG Homopolymer
1.0 g (2%)
0.001%
479 1186 (8.2)
760
ESG Homopolymer
1.0 g (2%)
0.0005%
468 1124 (5.0)
697
__________________________________________________________________________
.sup.1 Grams and mole % ester side groups (i.e. moles ester side group
repeat units/moles of PBT repeat units .times. 100) added to 56.9 g PBT
resin, unless noted.
.sup.2 Mole % lithium stearate is moles lithium stearate/mole PBT repeat
units .times. 100.
.sup.3 Initial Torque at 3 mins, before addition of polycarbonate resin o
catalyst, final Torque at 20 mins, after 17 min for resin coreaction, and
maximum torque, with time in minutes of the maximum.
.sup.4 Control, 59. g Valox .RTM. 315 only
.sup.5 Control, 59 g of Valox .RTM. 315 and catalyst
.sup.6 Control, Valox .RTM. 315, catalyst and standard BPA polycarbonate
homopolymer, (General Electric Co.), with IV = 0.500 dl/g
.sup.7 1/1 copolycarbonate of BPA and methyl2,4-dihydroxybenzoate with IV
= 0.672 dl/g (Preparation 1.).
.sup.8 Homopolycarbonate of methyl2,4-dihydroxybenzoate with IV = 0.551
dl/g (Preparation 2.).
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